I was wanting to know what you all thought the best technique is to process email addresses entered in my form. Should I do it in JavaScript, or should I have my web server do it -- however that works. It's just a simple 1-field collection.

All form field validation MUST be done on the server after the form is submitted. If you don't validate on the server then people can submit garbage in the form and you'd never know.

Any JavaScript validation added to the form is there simply to make it easier for some of those filling out the form as they can discover mistakes prior to submitting the form. It doesn't prevent people deliberately entering garbage as they can always turn JavaScript off.

Your question to Stephen depends on the language you're using. Try searching Google for +form +field +validation +[language you are coding in, for example PHP]. Hope that helps you to learn, there's no way you will effectively learn an answer to your question with a simple response on this forum. Please beware there are likely many more security concerns that you will need to address in your code as well, especially if you store submissions in a database (e.g. SQL injection attack prevention, etc.).